Dual-function light guide for lcd backlight

ABSTRACT

A light emitter/sensor includes a lamp, a light sensor, a light guide, and a light controller. The light guide has a pair of opposite ends and is optically-coupled to the lamp and the light sensor at one of the ends. The light guide is configured to convey light emitted from the lamp to the other end of the light guide, and from that other end to the light sensor. The light controller is coupled to the lamp and the light sensor and is configured to flash the lamp and to determine the intensity of light at that other end of the light guide, via the light guide and the light sensor, during an interval between the flashes.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 11/066,451, entitled Dual-Function Light Guide for LCDBacklight”, filed Feb. 28, 2005, the contents of which are incorporatedherein by reference.

FIELD OF THE INVENTION

The invention described herein relates to a mechanism for controllingvisualization of information rendered on the display device of aportable computing device. In particular, the invention described hereinrelates to a method and apparatus for controlling the backlightintensity of a liquid crystal display (LCD), based on the intensity ofambient light detected at the portable computing device.

BACKGROUND OF THE INVENTION

The conventional portable computing device, such as a personal dataassistant (PDA) or wireless telephone, has a liquid crystal display(LCD), a LCD backlight, and a keyboard/keypad. Typically, the displaybacklight is enabled when the device is powered on or when a key on thekeyboard/keypad is depressed. The intensity of light produced by thebacklight is factory set to a fixed level that allows the informationdisplayed on the LCD to be viewable in moderate ambient light levels.However, the backlight tends to be excessively bright at dim ambientlight levels, and insufficiently bright at very bright ambient lightlevels. In both of these situations, the clarity of the informationdisplayed on the LCD is comprised. Accordingly, attempts have been madeto make the information displayed on a LCD more readily viewable over awider range of ambient light levels.

For instance, Keiji (Patent Abstracts of Japan, Pub. No. 11-260572)describes a lighting system that changes the illumination level of theLCD, based on the intensity of ambient light detected. In oneembodiment, the lighting system comprises a liquid crystal displayhaving a Light Emitting Diode (LED) backlight and a light guide; a lightsensor disposed at an end face of the light guide; and control means forvarying the intensity of light emitted by backlight. The light sensormeasures the luminous energy at two or more wavelengths. The controlmeans determines the energy of light measured by the light sensor, whilemomentarily setting the radiant output energy of the backlight to zero.The control means then sets the radiant output energy of the backlightbased on the energy of light so measured.

Since the light sensor is disposed within the LCD, the light sensor isnot prone to erroneous intensity measurements resulting from dirtcontaminating the optical surface of the sensor. However, incorporatingthe light sensor into the LCD increases the manufacturing cost of theLCD. Therefore, there remains a need for an improved mechanism forrendering the information displayed on a LCD more readily viewable overa wide range of ambient light levels.

SUMMARY OF THE INVENTION

In accordance with one aspect of this disclosure, there is provided alight emitter/sensor that comprises a lamp, a light sensor, a lightguide, and a light controller. The light guide has a pair of oppositeends and is optically-coupled to the lamp and the light sensor at one ofthe ends. The light guide is configured to convey light emitted from thelamp to the other end of the light guide, and from that other end to thelight sensor. The light controller is coupled to the lamp and the lightsensor and is configured to flash the lamp and to determine theintensity of light at that other end of the light guide, via the lightguide and the light sensor, during an interval between the flashes.

In accordance with another aspect of this disclosure, there is provideda portable computing device that comprises a housing (that includes anexternal surface), and a display device supported by the housing. Thedisplay device includes illumination means for improved visualization ofinformation rendered on the display device. The portable computingdevice also comprises a lamp, a light sensor and a light guide that aredisposed within the housing. The light guide has a pair of oppositeends, and is optically-coupled to the lamp and the light sensor at oneof the ends and terminates at the external surface at the other end ofthe light guide. The light guide is configured to convey light emittedfrom the lamp to the external surface, and from the external surface tothe light sensor. The light controller is coupled to the lamp, the lightsensor and the illumination means. The light controller is configured toflash the lamp, to determine the intensity of ambient light at theexternal surface via the light conduit and the light sensor during aninterval between the flashes, and to adjust an intensity of lightemitted by the illumination means in accordance with the determinedambient light intensity.

The light guide may have a substantially Y-shape. In one implementation,the light guide has a pair of branches that terminate at the one end ofthe light guide, and a trunk that terminates at the other end of thelight guide, the branches being optically-coupled to the trunk. The lampmay be optically-coupled to one of the branches at the one end of thelight guide, and the light sensor may be optically-coupled to another ofthe branches at that one end of the light guide. The lightemitter/sensor may also comprise a lens that is optically-coupled to thetrunk at the other end of the light guide. The lens may be secured tothe housing and optically-coupled to the trunk at that other end of thelight guide.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a front plan view of the portable computing device, accordingthe invention described herein;

FIG. 2 is a schematic view of the portable computing device, depictingthe communication pathways existing between the data processing means,the event notifier, the LCD display, and the data input means of theportable computing device depicted in FIG. 1;

FIG. 3 is a schematic view of the interior of the portable computingdevice, depicting the event notification lamp, the light conduit and thelight sensor of one embodiment of the event notifier;

FIG. 4 is an exploded perspective view of another embodiment of theinvent notifier, in which the light conduit and the light sensor of theevent notifier are integrated with the light guide of the LCD display;

FIG. 5 is a schematic view depicting functional details of the portablecomputing device;

FIG. 6 is a schematic view depicting the communication pathways existingbetween the light controller, the event notifier, the display devicebacklight and the keyboard backlight of the portable computing device;

FIG. 7 is a flowchart depicting, by way of overview, the method ofcontrolling the illumination of the display device implemented in theportable computing device;

FIG. 8 is a a flowchart depicting, in detail, the method of illuminationcontrol of the display device implemented in the portable computingdevice having a transmissive LCD display; and

FIG. 9 is a flowchart depicting, in detail, the method of illuminationcontrol of the display device implemented in the portable computingdevice having a reflective, trans-reflective or transmissive LCDdisplay.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown a portable computing device,denoted generally as 100, provided according to one aspect of theinvention. The portable computing device 100 includes a display 122, afunction key 146, and data processing means 102 (not shown) disposedwithin a common housing 101. The display 122 comprises a backlit displayhaving a variable-intensity backlight, and the data processing means 102is coupled to the backlight of the display 122 and controls theintensity of light produced by the backlight.

In one embodiment, the backlit display 122 comprises a backlittransmissive LCD display, and the function key 146 operates as acombination power on/off switch and display backlight on/off switch.Alternately, in another embodiment, the backlit display 122 comprises abacklit reflective or trans-reflective LCD display, and the function key146 operates as a master backlight on/off switch.

As shown in FIG. 2, the data processing means 102 of the portablecomputing device 100 is in communication with the display 122 and theevent notifier 162. As will be described, the data processing means 102comprises a microprocessor 138, and a memory 124, 126 (disposed withinthe housing 101). The memory 124, 126 carries computer processinginstructions which, when accessed from the memory 124, 126 and executedby the microprocessor 138, cause the data processing means to performthe method which will be described in further detail below.

In addition to the display 122 and the event notifier 162, the portablecomputing device 100 includes user data input means for inputting datato the data processing means. Further, the data processing means 102 isin communication with the function key 146 and the user data inputmeans. Preferably, the user data input means includes a keyboard 132, athumbwheel 148 and an escape key 160. Preferably, the keyboard 132includes a keyboard backlight. Further, preferably the backlight for thekeyboard 132 is operable independently of the backlight for the display122.

In a first embodiment, the portable computing device 100 includes acavity (not shown) opening into the interior of the housing 101 from theexterior surface of the housing 101. Preferably, the cavity terminatesat the exterior housing surface proximate the display 122. In addition,if the portable computing device 100 has telephony capabilities,preferably the portable computing device 100 includes a speaker grille134 and a microphone grille 136, as shown in FIG. 1. Typically, thespeaker and microphone grilles 134, 136 each comprise one or moreapertures formed in the housing 101.

Further, as shown in FIG. 1, preferably the portable computing device100 includes a translucent lens 164 secured to the exterior housingsurface and enclosing the cavity. As shown, the lens 164 is disposedproximate the display 122. As will be explained, this position allowsthe data processing means 102 to detect the intensity of ambient lightfalling on the display 122. Preferably, the lens 164 is disposed abovethe display 122, adjacent the uppermost end of the portable computingdevice 100. Optionally, the lens 164 may be disposed below the display122, between the lowermost end of the display 122 and the uppermost endof the keyboard 132.

As shown in FIG. 3, in the first embodiment the event notifier 162comprises an event notification lamp 166 and a light conduit 168disposed within the housing 101. Typically, the event notification lamp166 comprises a light emitting diode (LED). The light conduit 168 istypically disposed within the aforementioned cavity. Further, the lightconduit 168 is optically-coupled at one end to the event notificationlamp 166, and terminates at the external surface of the housing 101 inorder to convey light between the event notification lamp 166 and theexternal surface. Preferably, the light conduit 168 comprises a lightguide that extends between the event notification lamp 166 and the lens164. Alternately, the light conduit 168 may simply comprise theaforementioned cavity, and extends between the event notification lamp166 and the speaker or microphone grille 134, 136.

In addition to the event notification lamp 166 and the light conduit168, preferably the event notifier 162 also includes an ambient lightsensor 170 optically-coupled to the light conduit 168 for measuring theintensity of the light in the light conduit 168. As will be appreciated,since the light conduit 168 terminates at the external surface of thehousing 101, the light sensor 170 is able to provide an indication ofthe intensity of ambient light external to the housing 101. Further,since the light conduit 168 typically terminates at the exterior housingsurface proximate the display 122, the light sensor 170 is able toprovide an indication of the intensity of ambient light falling on thedisplay 122.

It should be understood, however, that the light sensor 170 of theforegoing embodiment is not an essential feature of the invention.Rather, in one variation, the light sensor 170 is eliminated, and theintensity of ambient light is measured via a suitable event notificationlamp 166.

A second embodiment of the invention is depicted in FIG. 4, in which theevent notifier 162 is integrated with the display 122. As shown, thedisplay 122 comprises a planar light diffusing film 176, a planar lightreflecting layer 172, a planar light guide 174 disposed between thelight diffusing film 176 and the light reflecting layer 172, a planarliquid crystal module 180, a planar light intensifying layer 178disposed between the light diffusing film 176 and the liquid crystalmodule 180, and a plurality of backlight LEDs 182 optically-coupled toone edge of the light guide. The light reflecting layer 172, the lightguide 174, the light diffusing film 176, the light intensifying layer178, the liquid crystal module 180, and the backlight LEDs 182 are allretained within and supported by the housing 101 of the portablecomputing device 100. The liquid crystal module 180 iselectrically-coupled to the data processing means 102 to thereby allowthe data processing means 102 to present information on the display 122.

In the second embodiment, the event notification lamp 166 and the lightconduit 168 of the event notifier 162 are not required. Although, in thesecond embodiment, the event notifier 162 includes the ambient lightsensor 170, the ambient light sensor 170 is optically-coupled to thelight guide 174 of the display 122. As shown, preferably the ambientlight sensor 170 is coupled to the same edge of the light guide 174 asthe backlight LEDs 182, although other orientations/configurations areintended to be encompassed by the invention described herein. The lightguide 174 acts as a light conduit that not only directs light from thebacklight LEDs 182 to the liquid crystal module 178 (therebyilluminating the information depicted on the liquid crystal module 178),but also directs the ambient light that falls on the display 122 towardsthe ambient light sensor 170. As will become apparent, this embodimentallows the data processing means 102 to more accurately detect theintensity of ambient light falling on the display 122.

Typically, the portable computing device 100 is a two-way wirelesscommunication device having at least voice and data communicationcapabilities. Further, preferably the portable computing device 100 hasthe capability to communicate with other computer systems on theInternet. Depending on the exact functionality provided, the wirelessportable computing device 100 may be referred to as a data messagingdevice, a two-way pager, a wireless e-mail device, a cellular telephonewith data messaging capabilities, a wireless Internet appliance, or adata communication device, as examples.

FIG. 5 depicts functional details of the portable computing device 100.Where the portable computing device 100 is enabled for two-waycommunication, it will incorporate a communication subsystem 111,including both a receiver 112 and a transmitter 114, as well asassociated components such as one or more, preferably embedded orinternal, antenna elements 116 and 118, local oscillators (LOs) 113, anda processing module such as a digital signal processor (DSP) 120. Aswill be apparent to those skilled in the field of communications, theparticular design of the communication subsystem 111 will be dependentupon the communication network in which the device is intended tooperate. For example, the portable computing device 100 may include acommunication subsystem 111 designed to operate within the Mobitex™mobile communication system, the DataTAC™ mobile communication system,GPRS network, UMTS network, EDGE network or CDMA network.

Network access requirements will also vary depending upon the type ofnetwork 119. For example, in the Mobitex and DataTAC networks, theportable computing device 100 is registered on the network using aunique identification number associated with each portable computingdevice. In UMTS and GPRS networks, and in some CDMA networks, however,network access is associated with a subscriber or user of the portablecomputing device 100. A GPRS portable computing device thereforerequires a subscriber identity module (SIM) card in order to operate ona GPRS network, and a RUIM in order to operate on some CDMA networks.Without a valid SIM/RUIM card, a GPRS/UMTS/CDMA portable computingdevice may not be fully functional. Local or non-network communicationfunctions, as well as legally required functions (if any) such as “911”emergency calling, may be available, but the portable computing device100 will be unable to carry out any other functions involvingcommunications over the network. The SIM/RUIM interface 144 is normallysimilar to a card-slot into which a SIM/RUIM card can be inserted andejected like a diskette or PCMCIA card. The SIM/RUIM card can haveapproximately 64K of memory and hold many key configuration 151, andother information 153 such as identification, and subscriber relatedinformation.

When required network registration or activation methods have beencompleted, the portable computing device 100 may send and receivecommunication signals over the network 119. Signals received by antenna116 through communication network 119 are input to receiver 112, whichmay perform such common receiver functions as signal amplification,frequency down conversion, filtering, channel selection and the like,and in the example system shown in FIG. 5, analog to digital (A/D)conversion. A/D conversion of a received signal allows more complexcommunication functions such as demodulation and decoding to beperformed in the DSP 120. In a similar manner, signals to be transmittedare processed, including modulation and encoding for example, by DSP 120and input to transmitter 114 for digital to analog conversion, frequencyup conversion, filtering, amplification and transmission over thecommunication network 119 via antenna 118. DSP 120 not only processescommunication signals, but also provides for receiver and transmittercontrol. For example, the gains applied to communication signals inreceiver 112 and transmitter 114 may be adaptively controlled throughautomatic gain control algorithms implemented in DSP 120.

The portable computing device 100 preferably includes a microprocessor138 which controls the overall operation of the device. Communicationfunctions, including at least data and voice communications, areperformed through communication subsystem 111. Microprocessor 138 alsointeracts with further device subsystems such as the display 122, flashmemory 124, random access memory (RAM) 126, auxiliary input/output (I/O)subsystems 128, serial port 130, keyboard 132, speaker 134, microphone136, a short-range communications subsystem 140 and any other devicesubsystems generally designated as 142.

Some of the subsystems shown in FIG. 5 perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 132 and display122, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions such as a calculator or tasklist.

Operating system software used by the microprocessor 138 is preferablystored in a persistent store such as flash memory 124, which may insteadbe a read-only memory (ROM) or similar storage element (not shown).Those skilled in the art will appreciate that the operating system,specific device applications, or parts thereof, may be temporarilyloaded into a volatile memory such as RAM 126. Received communicationsignals may also be stored in RAM 126.

As shown, the flash memory 124 can be segregated into different areasfor both computer programs 158 and program data storage 150, 152, 154and 156. These different storage types indicate that each program canallocate a portion of flash memory 124 for their own data storagerequirements.

Microprocessor 138, in addition to its operating system functions,preferably enables execution of software applications on the portablecomputing device. The operating system software and the softwareapplications comprises computer processing instructions which, whenaccessed from the flash memory 124 and the RAM 126 and executed by themicroprocessor 138, define the aforementioned data processing means 102.A predetermined set of applications that control basic operations,including at least data and voice communication applications forexample, will normally be installed on the portable computing device 100during manufacturing.

Another such software application comprises a light controller 184 thatcontrols the backlight 182 of the backlit display 122. As shown in FIG.6, the light controller 184 is in communication with the light sensor170, and the display backlight 182 and the keyboard backlight 183. Also,in the first embodiment of the event notifier 162, the light controller184 is in communication with the event notification lamp 166. The lightcontroller 184 uses the light sensor 170 to determine the intensity ofambient light external to the housing 101. Also, the light controller184 is configured to adjust the intensity of light emitted by thedisplay backlight 182 and the keyboard backlight 183 in accordance withthe determined ambient light intensity.

The light controller 184 also controls the illumination of the eventnotification lamp 166 in accordance with one or more predefined events.For instance, the light controller 184 may be configured to flash theevent notification lamp 166 when the data processing means 102 is in asleep state. The light controller 184 may be configured to flash theevent notification lamp 166 when an e-mail message or a telephone callis received at the portable computing device 100. Other suitable eventsare intended to be encompassed by the invention described herein.

Returning again to FIG. 5, another software application may be apersonal information manager (PIM) application having the ability toorganize and manage data items relating to the user of the portablecomputing device such as, but not limited to, e-mail, calendar events,voice mails, appointments, and task items. Naturally, one or more memorystores would be available on the portable computing device to facilitatestorage of PIM data items. Such PIM application would preferably havethe ability to send and receive data items, via the wireless network119.

In a preferred embodiment, the PIM data items are seamlessly integrated,synchronized and updated, via the wireless network 119, with the user'scorresponding data items stored or associated with a host computersystem. Further applications may also be loaded onto the portablecomputing device 100 through the network 119, an auxiliary I/O subsystem128, serial port 130, short-range communications subsystem 140 or anyother suitable subsystem 142, and installed by a user in the RAM 126 orpreferably a non-volatile store (not shown) for execution by themicroprocessor 138. Such flexibility in application installationincreases the functionality of the device and may provide enhancedon-device functions, communication-related functions, or both. Forexample, secure communication applications may enable electroniccommerce functions and other such financial transactions to be performedusing the portable computing device 100.

In a data communication mode, a received signal such as a text messageor web page download will be processed by the communication subsystem111 and input to the microprocessor 138, which preferably furtherprocesses the received signal for output to the display 122, oralternatively to an auxiliary I/O device 128. A user of the portablecomputing device 100 may also compose data items such as email messagesfor example, using the keyboard 132, which is preferably a completealphanumeric keyboard or telephone-type keypad, in conjunction with thedisplay 122 and possibly an auxiliary I/O device 128. Such composeditems may then be transmitted over a communication network through thecommunication subsystem 111.

For voice communications, overall operation of the portable computingdevice 100 is similar, except that received signals would preferably beoutput to a speaker 134 and signals for transmission would be generatedby a microphone 136. Alternative voice or audio I/O subsystems, such asa voice message recording subsystem, may also be implemented on theportable computing device 100. Although voice or audio signal output ispreferably accomplished primarily through the speaker 134, display 122may also be used to provide an indication of the identity of a callingparty, the duration of a voice call, or other voice call relatedinformation for example.

Serial port 130 in FIG. 5, would normally be implemented in a personaldigital assistant (PDA)-type portable computing device for whichsynchronization with a user's desktop computer (not shown) may bedesirable, but is an optional device component. Such a port 130 wouldenable a user to set preferences through an external device or softwareapplication and would extend the capabilities of the portable computingdevice 100 by providing for information or software downloads to theportable computing device 100 other than through a wirelesscommunication network. The alternate download path may for example beused to load an encryption key onto the device through a direct and thusreliable and trusted connection to thereby enable secure devicecommunication.

Other communications subsystems 140, such as a short-rangecommunications subsystem, is a further optional component which mayprovide for communication between the portable computing device 100 anddifferent systems or devices, which need not necessarily be similardevices. For example, the subsystem 140 may include an infrared deviceand associated circuits and components or a Bluetooth™ communicationmodule to provide for communication with similarly enabled systems anddevices.

FIG. 7 is a flow chart that depicts, by way of overview, the sequence ofsteps performed by the light controller 184 according to the invention.Initially, the portable computing device 100 is in an inactive state,and the display backlight 182 and the keyboard backlight 183 are at aminimum/off intensity. Typically, the light controller 184 flashes theevent notification lamp 166 to notify the user that the portablecomputing device 100 is not off, but is instead inactive. The portablecomputing device 100 remains in the inactive state until the dataprocessing means 102 detects a data event. Suitable data events includeactivity at the data input means (pressing a key on the keyboard 132,rotating the thumbwheel 148 or depressing the escape key 160), anincoming message (such as a telephone call or e-mail message), or apredetermined event (such as a scheduled meeting or task).

When the portable computing device 100 exits from the inactive state, atstep 400 the light controller 184 determines the ambient light level atthe computing device 100, via the ambient light sensor 170. The lightcontroller 184 determines the ambient light intensity by measuring theintensity of the light in the light guide 168, 174 with the light sensor170.

Preferably, the light controller 184 is configured to determine theambient light intensity during an interval when the intensity of thelight emitted by the display and keyboard backlights 182, 183 is at aminimum. Further, preferably the light controller 184 is configured todetermine the ambient light intensity during an interval when the lightcontroller 184 has extinguished the event notification lamp 166, forexample between flashes of the event notification lamp 166.

At step 402, the light controller 184 sets the intensity of the displaybacklight 182 to an intensity level that is sufficient for viewinginformation on the display 122 under the determined lighting conditions.Typically, this latter step involves automatically setting the intensityof light to a first intensity when the determined light level is greaterthan a first level, and automatically setting the intensity of light toa second intensity less than the first intensity when the determinedlight level is less than the first level.

In one embodiment, the backlit display 122 is a transmissive LCDdisplay, and the intensity adjusting step also involves setting theintensity of light to a third intensity less than the second intensitywhen the determined light level is less than a second level, the secondlevel being lower than the first level. In another embodiment, thebacklit display 122 is a reflective or trans-reflective LCD display, andthe intensity adjusting step also involves setting the intensity oflight to a third intensity less than the second intensity when thedetermined light level is greater than a second level, the second levelbeing greater than the first level.

In one variation of these embodiments, the intensity adjusting stepinvolves illuminating the keyboard 132 at a first candela level when thedetermined light level is greater than the first level, and illuminatingthe keyboard 132 at a second candela level less than the first candelalevel when the determined light level is less than the first level.Further, the intensity adjusting step involves illuminating the keyboard132 at a third candela level less than the second candela level when thedetermined light level is greater than the first level.

FIG. 8 is a flow chart that depicts, in detail, the sequence of stepsperformed by the data processing means 102 on a portable computingdevice 100 having a transmissive LCD display 122.

Initially, at step 500, the portable computing device 100 is in aninactive state, such as a sleep state; and the display backlight 182 andthe keyboard backlight 183 are at a minimum intensity, such as off.Typically, the light controller 184 flashes the event notification lamp166 to notify the user that the portable computing device 100 is notoff, but is instead inactive.

At step 502, the data processing means 102 waits for activity on thedata input means, such as a depression of a key on the keyboard 132,rotation of the thumbwheel 148 or depression of the escape key 160. Ifthe user of the portable computing device 100 activates the data inputmeans, the data processing means 102 exits the inactive state, andprocessing transitions to step 504.

Alternately, in one variation, the data processing means 102 exits theinactive state in response to activity occurring on one of the computerprograms 158. For instance, the data processing means 102 may exit theinactive state when an e-mail message or a telephone call is received onthe portable computing device 100.

Typically, when the user depresses a key on the keyboard 132 or theescape key 160, the data processing means 102 processes the activity asa key stroke, and uses the key stroke as a data input to one of thecomputer programs 158. Further, typically when the user rotates ordepresses the thumbwheel 148, the data processing means 102 processesthe activity as a navigation input to the operating system or one of thecomputer programs 158. However, at step 502, since the activity on thedata input means is used to exit the portable computing device 100 fromthe inactive state, the data processing means 102 suppresses the normaleffect (data input, navigation input) of the activity.

At step 504, the light controller 184 determines the ambient light levelat the portable computing device 100. The light controller 184determines the ambient light intensity by measuring the intensity of thelight in the light guide 168, 174 with the light sensor 170. Preferably,the light controller 184 determines the ambient light intensity duringthe interval between flashes of the event notification lamp 166, i.e.when the light controller 184 has momentarily extinguished the eventnotification lamp 166.

At step 506, the light controller 184 compares the determined lightlevel against a first predetermined threshold level. Typically, thefirst predetermined threshold level is intermediate an illuminationlevel corresponding to exposure to sunlight, and an illumination levelcorresponding to dusk.

If the determined light level is greater than the first predeterminedthreshold level, at step 508 the light controller 184 sets the intensityof the display backlight 182 to a first intensity level. Typically, thefirst intensity level is the maximum display backlight intensity. Inaddition, preferably the light controller 184 keeps the keyboard/keypadbacklight 183 off.

If the determined light level is not greater than the firstpredetermined threshold level, at step 510 the light controller 184compares the determined light level against a second predeterminedthreshold level. Typically, the second predetermined threshold level isintermediate the illumination level corresponding to dusk, and anillumination level corresponding to night.

If the determined light level is less than the second predeterminedthreshold level, at step 512 the light controller 184 sets the intensityof the display backlight 182 to a third intensity level. Typically, thethird intensity level is a dim backlight intensity that is slightlygreater than the minimal/off intensity level. The dim backlightintensity is sufficient to allow the information displayed on thedisplay 122 to be viewed at night, without “blinding” the user of theportable computing device 100.

In addition, preferably the light controller 184 sets the intensity ofthe keyboard/keypad backlight 183 to a dim keyboard intensity (brighterthan off). As above, the dim keyboard intensity is sufficient to allowthe key identifier information printed on the keys to be viewed atnight, without “blinding” the user of the portable computing device 100.

However, if the determined light level is not less than the secondpredetermined threshold level (but is less than the first predeterminedthreshold level), at step 514 the light controller 184 sets theintensity of the display backlight 182 to a second intensity level.Typically, the second intensity level is a level intermediate the first(maximum) backlight intensity and the third (dim) backlight intensity.The second backlight intensity is sufficient to allow the informationdisplayed on the display 122 to be viewed at dusk, again without“blinding” the user of the portable computing device 100.

In addition, preferably the light controller 184 sets the intensity ofthe keyboard/keypad backlight 183 to a bright backlight intensity(typically the maximum backlight intensity).

Thereafter, at step 516, the data processing means 102 waits a firstpredetermined time period for activity at the data input means (eg.pressing a key on the keyboard 132, rotating the thumbwheel 148 ordepressing the escape key 160) or for an e-mail message or a telephonecall being received on the portable computing device 100. If the dataprocessing means 102 detects such activity within the firstpredetermined time period (typically about 10 seconds), processingreturns to step 504.

However, if the first predetermined time period expires without any suchactivity, at step 518 the light controller 184 begins to graduallyreduce the intensity of the display backlight 182, so as to provide awarning to the user of the portable computing device 100 that thedisplay backlight is about to be turned off. In addition, preferably thelight controller 184 also turns off the keyboard backlight 183.

Thereafter, at step 520, the data processing means 102 waits a secondpredetermined time period for activity at the data input means or for ane-mail message or a telephone call being received on the portablecomputing device 100. If the data processing means 102 detects suchactivity within the second predetermined time period (typically about 15seconds), processing returns to step 504.

However, if the second predetermined time period expires without anysuch activity, at step 522 the light controller 184 turns off thedisplay backlight 182.

Thereafter, at step 524, the data processing means 102 waits a thirdpredetermined time period for activity at the data input means or for ane-mail message or a telephone call being received on the portablecomputing device 100. If the data processing means 102 detects suchactivity within the third predetermined time period (typically about 60seconds), processing returns to step 504.

However, if the third predetermined time period expires without any suchactivity at the data input means, processing returns to step 502 and theportable computing device 100 returns to the inactive/sleep state.

FIG. 9 is a flow chart that depicts, in detail, the sequence of stepsperformed by the light controller 184 on a portable computing device 100having a reflective, trans-reflective or transmissive LCD display 122.

Initially, at step 600, the portable computing device 100 is in aninactive state, such as a sleep state; and the display backlight 182 andthe keyboard backlight 183 are at a minimum intensity, such as off.

At step 602, the data processing means 102 waits for activity on thedata input means, such as by pressing a key on the keyboard 132,rotating the thumbwheel 148 or depressing the escape key 160. If theuser of the portable computing device 100 activates the data input meansthe portable computing device 100 exits the inactive state, andprocessing jumps to step 604.

Typically, when the user depresses a key on the keyboard 132 or theescape key 160, the data processing means 102 processes the activity asa key stroke, and uses the key stroke as a data input to one of thecomputer programs 158. Further, typically when the user rotates ordepresses the thumbwheel 148, the 1 data processing means 102 processesthe activity as a navigation input to the operating system or one of thecomputer programs 158. However, at step 602, since the activity on thedata input means is used to exit the portable computing device 100 fromthe inactive state, the data processing means 102 suppresses the normaleffect (data input, navigation input) of the activity.

At step 604, the light controller 184 determines the ambient light levelat the portable computing device 100, via the ambient light sensor 170.At step 606, the light controller 184 compares the determined lightlevel against a first predetermined threshold level. Typically, thefirst predetermined threshold level is intermediate an illuminationlevel corresponding to dusk, and an illumination level corresponding tonight.

If the determined light level is less than the first predeterminedthreshold level, at step 608 the light controller 184 sets the intensityof the display backlight 182 to a second intensity level. Typically, thesecond intensity level is a dim backlight intensity that is slightlygreater than the minimal/off intensity level. The dim backlightintensity is sufficient to allow the information displayed on thedisplay 122 to be viewed at night, without “blinding” the user of theportable computing device 100.

In addition, preferably the light controller 184 sets the intensity ofthe keyboard/keypad backlight 183 to a dim keyboard intensity (brighterthan off). As above, the dim keyboard intensity is sufficient to allowthe key identifier information printed on the keys to be viewed atnight, without “blinding” the user of the portable computing device 100.

If the determined light level is not less than the first predeterminedthreshold level, at step 610 the light controller 184 compares thedetermined light level against a second predetermined threshold level.Typically, the second predetermined threshold level is intermediate anillumination level corresponding to exposure to sunlight, and theillumination level corresponding to dusk.

If the determined light level is greater than the second predeterminedthreshold level, at step 612 the light controller 184 sets the intensityof the display backlight 182 to a third intensity level. Typically, thethird intensity level is the minimal/off intensity level. In addition,preferably the light controller 184 turns off the keyboard/keypadbacklight 183.

However, if the determined light level is not greater than the secondpredetermined threshold level (but is not less than the firstpredetermined threshold level), at step 614 the light controller 184sets the intensity of the display backlight 182 to a first intensitylevel. Typically, the first intensity level is the maximum backlightintensity. The first backlight intensity is sufficient to allow theinformation displayed on the display 122 to be viewed at dusk, againwithout “blinding” the user of the portable computing device 100.

In addition, preferably the light controller 184 sets the intensity ofthe keyboard/keypad backlight 183 to a bright backlight intensity(typically the maximum backlight intensity).

Thereafter, at step 616, the data processing means 102 waits a firstpredetermined time period for activity at the data input means (eg.pressing a key on the keyboard 132, rotating the thumbwheel 148 ordepressing the escape key 160) or for an e-mail message or a telephonecall being received on the portable computing device 100. If the dataprocessing means 102 detects such activity within the firstpredetermined time period (typically about 10 seconds), processingreturns to step 604.

However, if the first predetermined time period expires without any suchactivity, at step 618 the light controller 184 begins to graduallyreduce the intensity of the display backlight 182, so as to provide awarning to the user of the portable computing device 100 that thedisplay backlight is about to be turned off. In addition, preferably thelight controller 184 also turns off the keyboard backlight 183.

Thereafter, at step 620, the data processing means 102 waits a secondpredetermined time period for activity at the data input means or for ane-mail message or a telephone call being received on the portablecomputing device 100. If the data processing means 102 detects suchactivity within the second predetermined time period (typically about 15seconds), processing returns to step 604.

However, if the second predetermined time period expires without anysuch activity, at step 622 the light controller 184 turns off thedisplay backlight 182.

Thereafter, at step 624, the data processing means 102 waits a thirdpredetermined time period for activity at the data input means or for ane-mail message or a telephone call being received on the portablecomputing device 100. If the data processing means 102 detects suchactivity within the third predetermined time period (typically about 60seconds), processing returns to step 604.

However, if the third predetermined time period expires without any suchactivity, processing returns to step 602 and the portable computingdevice 100 returns to the inactive/sleep state.

Variations on the foregoing embodiments are envisaged. For instance, inone variation, rather than the first, second and third intensity levelsbeing fixed, the data processing means 102 allows the user of theportable computing device 100 to set the intensity levels through thedata input means (such as through the thumbwheel 148). In anothervariation, rather than the first and second threshold levels beingfixed, the data processing means 102 allows the user of the portablecomputing device 100 to set the threshold levels through the data inputmeans (such as through the thumbwheel 148).

In yet another variation, the light controller 184 allows the user toturn the display backlight 182 on (maximum intensity) or off, bymomentarily depressing and releasing the function key 146. In stillanother variation, the light controller 184 allows the user to cyclethrough each combination of display backlight intensity level andkeyboard backlight intensity level by momentarily depressing andreleasing the function key 146. In other variation, the light controller184 allows the user to terminate the automatic dimming (at steps 518,618) by momentarily depressing and releasing the function key 146.

In another variation, the event notifier 162 includes the eventnotification lamp 166 and the light conduit 168 (of the firstembodiment), and the light guide 174 (of the second embodiment), withthe ambient light sensor 170 being coupled to both the light conduit 168and the light guide 174. With this variation, the ambient light sensor170 is able to measure the ambient light proximate the lens 164 and thedisplay 122, thereby providing a more accurate assessment of the ambientlight level.

1-10. (canceled)
 11. A handheld communications device, comprising: a display device, comprising: a display panel; a light guide coupled to the display panel; a light sensor, the light sensor configured to measure an intensity of ambient light, the light guide configured to direct light between the display panel and the light sensor; and a light source, optically coupled to the light guide, the light guide configured to direct light between the display panel and the light source; and a light controller coupled to the display panel and configured to adjust an intensity of light emitted by the light source in accordance with the measured ambient light intensity.
 12. The handheld communications device of claim 11, wherein the light sensor and the light source are provided at a common end of the light guide.
 13. The handheld communications device of claim 11, further comprising an event notifier, wherein the event notifier comprises the light sensor.
 14. The handheld communications device of claim 11, further comprising a user data input device coupled to the light controller, the user data input device comprising a keyboard and a keyboard backlight, wherein the light controller is configured to adjust an intensity of light emitted by the keyboard backlight in accordance with the measured ambient light intensity.
 15. The handheld communications device of claim 11, further comprising a housing, wherein the light guide is configured to convey light between the light source and an external surface of the housing.
 16. The handheld communications device of claim 15, wherein the light sensor is configured to measure the intensity of light at the external surface via the light guide, and the light controller is configured to adjust the intensity of emitted light in accordance with the measured external light intensity.
 17. The handheld communications device of claim 11, wherein the light source comprises a plurality of backlight LEDs.
 18. The handheld communications device of claim 11, wherein the light guide is a planar light guide.
 19. A method of illuminating information rendered on a display device of a handheld communications device, the display device comprising a display panel, a light guide coupled to the display panel, a light sensor, the light sensor configured to measure an intensity of ambient light, the light guide configured to direct light between the display panel and the light sensor, and a light source, optically-coupled to the light guide, the light guide configured to direct light between the display panel and the light source, the method comprising the steps of: measuring an intensity of ambient light using the light sensor; and adjusting an intensity of light emitted by the light source in accordance with the measured ambient light intensity.
 20. The method of claim 19, wherein the light sensor and the light source are provided at a common end of the light guide.
 21. The method of claim 19, wherein the handheld communications device further comprises an event notifier, wherein the event notifier comprises the light sensor.
 22. The method of claim 19, wherein the handheld communications device further comprises a user data input device, the user data input device comprising a keyboard and a keyboard backlight, and wherein the intensity adjusting step further comprises adjusting an intensity of light emitted by the keyboard backlight in accordance with the measured ambient light intensity.
 23. The method of claim 19, wherein the handheld communications device further comprises a housing, and wherein the intensity measuring step further comprises measuring the intensity of light external to the housing via the light guide and the light sensor.
 24. The method of claim 23, wherein the intensity adjusting step further comprises adjusting the intensity of emitted light in accordance with the measured external light intensity.
 25. The method of claim 19, wherein the light source comprises a plurality of backlight LEDs.
 26. The method of claim 19, wherein the light guide is a planar light guide. 